Top speed 530d

Hi all, I found out with my 530d (E39, BJ 02/00) that with Tacho 200 (if it goes downhill maybe 205) it’s over. Up to this speed it goes normally. The usual suspect (LMM) according to workshop or rather diagnostic device is allegedly not to blame. Does anyone have an idea where the fault devil could still be there? Thank you very much in advance, P.